It is known to coat spherical and like-shaped objects with various materials and for various purposes. For example, U.S. Pat. No. 2,833,241 discloses painting golf balls while same are levitated or suspended in an upwardly flowing airstream; and U.S. Pat. Nos. 3,112,220; 3,241,520 and 3,880,116 discloses coating pharmaceutical products with protective coatings in fluidized beds of upwardly flowing air, the coating materials being, e.g., sprayed upwardly through the bed in the fluidized airstream. It also is known to coat non-spherical articles to enhance resistance to corrosion (U.S. Pat. No. 3,961,098) and to coat articles such as piston rings by plasma arc technique to enhance the wear surfaces of the rings (U.S. Pat. No. 3,936,295). Holding various shaped articles to be coated, such as with paint or other materials in a rotating receptacle is known from, inter alia, U.S. Pat. Nos. 4,311,111 and 3,517,644.
One form of spherical objects to which it would be particularly desirable to apply an anti-wear and/or anti-corrosive coatings as well as thermally insulative coatings are ball bearings, especially ferrous based material ball bearings. Techniques as exemplified by the aforementioned prior art and such other methods as are known to us by which material coatings can be applied to various shaped objects would not be satisfactory for coating a ball bearing both from the standpoint of acceptable coating uniformity and application of such coatings without leaving a coating edge residue on the ball. Presence of an edge on the coating of a ball bearing is unsatisfactory in that the edge is an access point for corrosive attack on the ball structure and for the initiation of mechanical deterioration.